Photodynamic therapy (hereinafter referred to as PDT), is a relatively novel type treatment developed in the last ten years for certain types of cancer, including skin cancer and breast cancer. The PDT treatment is based on the systemic or topical administration of a tumor-localizing photosensitizer reagent, such as porphyrins, which after illumination and excitation with visible light in the presence of oxygen, give rise to highly reactive and cytotoxic molecular species. These cytotoxic molecular species damage sensitive targets within the tumor, producing cell death and subsequent tumor necrosis.
The early clinical work used a wide range of filtered and unfiltered light, sources, but it was concluded that a laser light was necessary in order to produce monochromatic light of the appropriate wavelength at high power levels which could be transmitted via a flexible fiber. The delivery dose will obviously depend on the area of tumor to be treated and the power of the laser. Generally a minimal delivery dose of 12 mW/cm.sup.2 is mentioned to be necessary, although there are cases where satisfactory clinical results have been obtained using also a lower dose. The total energy dose is quite empirical, but it is suggested that for superficial skin lesions, a total dose in the range of 25 to 50 J/cm.sup.2 may be appropriate, whereas for exophytic ulcerated lesions, a total dose of 100-200 J/cm.sup.2 is thought to be necessary.
To-day it is considered that PDT has to be introduced as the first arm of treatment of tumors on the human body.
A very recent publication WO 90/00420, describes an apparatus for a light delivery system, applicable to medical treatment techniques which rely on the illumination of body tissue in order to achieve photodynamic therapy and biostimulation. The apparatus comprises a source for illuminating the surface and means for scattering light reflected from the surface so that it can be directed back onto the surface. Preferably, the source for illuminating is a laser and the reflecting surface has a concave shape. Most preferably, the light source is the tip of an optical fiber which is arranged in a manner which could illuminate the diffusely reflective surface so that the light resulted from the laser is reflected towards the area to be treated. However, laser systems suffer from some important drawbacks being quite expensive, especially for an ambulatory apparatus, and the illumination obtained is characterized by its non-homogeneity. Moreover, there is no evidence whatsoever that for PDT treatment, there are required the specific qualities possessed by laser, as opposed to non-coherent conventional lamps, such as monochromacity or temporal coherence.
The use of laser diodes is claimed in the U.S. Pat. No. 4,930,504 for biostimulation of tissue. The apparatus used comprises an array of monochromatic radiation sources which provide a first wavelength of less than 830 nm, a second wavelength greater than 830 nm and a third wavelength greater than 900 nm.
Another recent U.S. Pat. No. 5,010,452 describes a therapeutic lamp for biostimulation with polarized light. The light source is mentioned that has to possess a power in the range of between 30 W and 300 W. The apparatus described seems to be quite complicated to be useful as an ambulatory device for the PDT treatment.
The above brief review of some references from the prior art, clearly indicates the long felt need for a simple apparatus useful for the PDT treatment.
It is an object of the present invention to provide a simple apparatus useful for the treatment of PDT. It is another object of the present invention to provide a simple apparatus which is capable to supply a broad band radiation, useful for an efficient treatment of PDT. It is yet another object of the present invention to provide a simple apparatus useful for the treatment of PDT, which does not require any skilled technician for its smooth operation.